Extraction of dyestuffs



Patented Feb. 10, 1931 UNITED STATES "PATENT OFFICE WILLIAM wmrnnnan, or-oUnBnaLAm), MARYLAND, Assronoa 'ro 'rrm onmlmsn oonroaArIoN or AMERIC A CORPORATION or DEL ARE EXTRACTION F DYESTUEFS 11o Drawing.

films and the like, may be bleached by chemical rocesses. In these bleaching processes the dyestufis themselves are destroyed and a the fibres, films, or the like are changed.physically and chemically to such an extent that their dyeing properties are altered and that the luster, strength, or elasticity may be impaired.

m This invention com rises a process for the extraction of dyestu s from artificial fibres, films, and the like, which is a physical process and results in a separation of the dye stufis and fibres without changing them '15 either chemically or physically. Thereafter the dyestufis may beused for-future dyeing and the fibres, films and the like may be used either without further change or they may be redyed or if desired they may be redis-- flilil solved and used for the. production of new fibres, films, or for other purposes.

While the invention is applicable particularly to artificial fibres, films and the like, made from cellulose ethers and cellulose W esters, and more especially to such products formed from cellulose acetate, it may be applied to other types of artificial fibres, films.

and the like. Also, notwithstanding the fact that it is particularly adapted for sulphoae ricinoleic acid dyestufis, it may be used in connection with other dyestufl's such as are insoluble in water but soluble in organic solvents and usually applied from an aqueous dispersion.

The invention herein claimed is a specific example of the invention disclosed in my copending application Serial No. 64,574, filed October 24, 1925, and in said other case it has been pointed out that a large number of dif-. W ferent' substances or solutions may be used for this purpose. The only essential feature is that the solution shall be a swelling agent for the fibres, films or the like and a solvent for the dyestufis. Some substanceshave both qualities, while in other cases it 'is-necessary to mix two substances in the solution since only one may be a swelling agent for the dye- (situfi's or only one may be a solvent for the yes.

Some substances will extract the dyestufis methods and with S. R

Application filed October 24, 1925. Serial m. 64,575.

It has been well known that artificial fibres,

by treatment of the material therewith in the cold. In other cases, thematerial and solution must be heated in order to obtain the most advantageous results. The temperature may vary somewhat according to the boiling point of the solvent em loyed, but

will usually be from about 54 to 2 C.

The solutions which are capable of removing the dyestuffs in the cold are much more powerful swelling agents for the fibres, films, and the like, and much greater care is therefore necessary to prevent disintegration or physical alterations thereof. When the treatment is carried out with solutions which need to be heated, the dyestufis will be extracted with properties substantially unchanged and the fibres or other artificial cellulosic material will be unaltered as regards chemical and physical pro erties.

The length of time of t e treatment will vary and it has' been found that successive treatments of about ten minutes with fresh solutions are more advantageous. The successive treatments may he carried out at gradually increasing temperatures. The particular mechanical means for carryin process isimmaterial and any suita le apparatus 'may be employed for the mechanical agitation of the cellulosic material and the extracting solutions.

The group of substances which it is desired to claim in' this application includes the chlorine derivatives of unsaturated hydrocarbons. Of this grou theremay be specified dichlorethylene, C Cl ;trichlorethylene, 0 1E101 perchlorethylene, (3 Gb, and the like. 0% these the preferable substance appears to be trichlorethylene.

If cellulose acetate yarn dyed b S. R. A. A dyestu s is mixed with trichlorethylene in the cold, no dyestufi's are extracted. 'llf the mixture is heated, the yarn swells gently and without any tendency to disintegrate, and the d estufis in the yarn enter into solution with the trichlorethylene. It is preferable to repeat the treatment a few times with fresh hot solutions and thereby all of the dyestuffs may be removed from the yarn, leavinglthe chemlcal and physical roperties of hot the yarn and the dyestu s unout the altered. Films composed of-cellulose acetate and similarly dyed may be treated in the same wa with similar results. 7

is stated above, it is preferable to employ a temperature of from about 54 to 72 C. in this treatment. If the yarn is treated for three ten minute periods with trichlorethylene alone, it will be found that an appreciable amount of the dyestuff will remain and if it is desired to remove this, a further treatment will be necessary.

However. if a small amount, preferably about 2% of acetone is added to the trichlorethylene, three ten minute treatments with this solution under the same temperature conditions as stated above will entirely remove the dyestuffs from the yarn without any change in the physical or chemical characteristics of either the yarn or the dyestuffs.

There may also be added to the solution of trichlorethylene or acetone, a small amount of benzene or similar substance. This appears to facilitate somewhat the operation.

The dichlorethylene may be used in the cold for the extraction of the dyestuffs, but it is such a powerful swelling agent that it tends to affect the luster and physical properties of the yarn, films, etc., unless the process is very carefully carried out.

As indicated above, b the use of trichlorethylene the dyes may e extracted, leaving the physical and chemical properties of the cellulosic material substantially unchanged.

There may be some slight change in the characteristics of the dyestuffs due to the following fact. These chlorine derivatives are subject to very gradual hydrolysis, especially when heated in the presence of moisture. The

free acids developed "by this hydrblysis will cry of the dyestuffs is of less importance than 1 the recovery of the fibres, films, and the like. There may be removed at the same time-with the dyestufis, oil, sizes, or other finishes which have been applied to the materials under treatment and this may necessitate certain purification before the dyestufis are again used. While the process is particularly ada ted to materials which have been dyed with R'. A. dyestufis and S. R. A. methods, it is also applicable to materials which have been dyed with other dyestufi's, particularly those which are applied to the yarn from a colloidal dis persion. Examples of such dyestuffs are:

Furthermore, the temperature conditions may vary since the highest temperature is the boiling point of the extracting medium and menace the lowest varies with the medium'employed. Temperaturesof from 28 to 72 C. have been found satisfactory.

It may be noted that the solutions referred to in the claims may he a solution of a single substance or solutions of a mixture of substances. The cellulosic materials may be either yarns, fabrics, films, or the like. It is obvious that the process may be applied to yarns or fabrics consisting solely of artificial cellulose material or to those consisting only in part of such material. In general, it may be stated that the invention is to be regarded as limited only by the scope of the appended claims.

I claim as my invention:

1. A process for the extraction of dyestuffs from dyed artificial cellulosic material which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes a chlorine derivative of an unsaturated aliphatic hydrocarbon.

2. A process for the extraction of dyestuffs from dyed artificial cellulosic material which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes a chlorine derivative of an unsaturated aliphatic hydrocan hon and acetone.

3. A process for the extraction of dyestuffs from dyed artificial cellulosic material which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes trichlorethylene.

4. A process for the extraction of dyestuffs from dyed artificial material formed from organic derivatives of cellulose which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes trichlorethylene and acetone.

5. A process for the extraction of dyestuffs from dyed artificial material formed from organic derivatives of cellulose which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes trichlorethylene and about 2% of acetone.

6. A process for the extraction of dyestuffs from dyed artificial material fori'ned from organic derivatives of cellulose which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuifs, and includes trichlorethylene, the treatment being carried out at from 54 to 72 C.

7. A process for the extraction of dyestuffs from dyed artificial material formed from organic derivativesof cellulose which comprises treating said material with a solution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs, and includes trichlorethylene and acetone, the treatment being carried out at from 54 to 72 C.

8. A process for the extraction of dyestuffs from dyed artificial material formed from organic derivatives of cellulose which comprises treating said material with a so-'. lution which is a swelling agent for the cellulosic material and a solvent for the dyestuffs. and includes triehlorethylene, acetone and benzene.

9. A process for the extraction of dyestuffs from dyed artificial material formed from organic derivatives of cellulose which comprises giving said material successive treatments with a solution which is a swelling agent for he cellulo sic material and a solvent forthc dyestuflts and includes trichlorethylene.

10.,A process for the extraction of dyestufls from dyed artificial material formed from organic derivatives of cellulose which comprises giving said material successive treatments at gradually increasing temperatures with a solution which is a swelling agent for the cellulosio material and a'solvent for the dyestuffs, and includes trichlorethylene and acetone.

11. A process for the extraction of dyestufls from dved material formed from cellulose acetate. which comprises treating said material with a solution which is a swelling agent for the cellulose acetate and a solvent for the dyestuffs, and includes a chlorine derivative of an unsaturated aliphatic hydrocarbon.

12. A process for the extraction of dye studs from dyed material formed from cellulose acetate. which comprises treating said material with a solution which is a swelling aszent for the cellulose acetate and a solvent for the dyestufls, and includes trichlorethylene.

131A process for the extraction of dyestuffs from dyed material formed from cellulose acetate, which comprises treating said 'material with a solution which is a swelling agent" for the cellulose acetate and a solvent for the dyestufls, and includes trichlorethylene and acetone. 4

14. A process for the extraction of dyestuffs from dyed material formed from cellulose acetate, which comprises giving said material successive treatments at. grad; ually increasing temperatures with a solution which is a swelling agent for the cellulose acetate and a solvent for the dyestufls, and includes a chlorine derivative of an unsaturated aliphatic hydrocarbon.

15. A process for the extraction of dyestufis from dyed material formed from cellulose acetate, which comprises giving said material successive treatments at gradually increasing temperatures with a solu- -tion which is a swelling agent for the'cellu- WILLIAM 

